为何体重反弹容易，减肥却这么困难?发表于《肥胖》(Obesity)杂志上的近期研究表明，实际上我们的身体机制抗拒体重减轻。节食时，人体的静息代谢率降低，当我们运动量很少时，燃烧的热量就很少。这项研究的发起人表示减肥需要“机警地与代谢适应过程作斗争”。
The study followed 14 participants of the US version of the TV show The Biggest Loser. The researchers found that, after six years, all but one of the contestants in their study had regained weight. On average, they weighed 20st 10lb (131.5kg), compared with the average starting weight of 23st 6lb (149kg) and the 14st 4lb (91kg) at which they finished the show.
这项研究跟踪调查了美国版的电视节目《超级减肥王》(The Biggest Loser)中的14位参与者。研究人员发现，六年后，这项研究中除一位参与者外，其他所有人的体重都反弹了。他们现在的平均体重是290磅(131.5千克)，而刚参加节目时的平均体重是328磅(149千克)，节目结束时的平均体重是200磅(91千克)。
The solution
解决方法.
Six years is a long time, and being, on average, 2st 10lb (17kg) lighter is not insignificant. But the odds were stacked against the participants. The study showed that, before the competition, the group burned a daily average of 2,600 calories at rest, but this fell to around 2,000 calories a day when it finished. Six years later, instead of creeping back up to its normal level, their resting rate had slowed further to 1,900 calories a day. On average, the resting metabolic rate was 500 calories a day less than you would expect for the age and body composition of the person. So, the contestants had to eat less to stay at their lower weight. While researchers knew that dieting reduces the resting metabolic rate to save energy, this study shows how savagely your body subverts weight loss.
六年的时间很长，平均每个人减重38磅(17kg)，其效果并不显著。但参与者减肥成功的机会不大。研究表明，在减肥比赛开始前，这群参与者每天不活动时平均能消耗2600卡。但节目结束时，他们每天不活动时大约只能消耗2000卡了。六年后，他们的静息代谢率进一步放缓，每天只能消耗1900卡，而没有回升到正常水平。考虑每个人的年龄和身体组成，他们平均的静息代谢率比期望的低500卡。所以，参与者必须减少食物摄入以保持较低体重。研究人员知道节食会降低身体的静息代谢率以储存能量，而这项研究表明了我们的身体机制疯狂地抗拒体重减少。
This was a small study without controls, though, and weight loss is influenced by factors such as genetics and hormones. Other studies show that some people are less affected than others. The report on The Biggest Loser participants cites another study showing that obese people who have weight-loss surgery seem to escape this metabolic adaptation. Somehow, the body resets to a new normal weight and the resting metabolic rate doesn’t fall. For the rest of us, being vigilant about what we eat, and building up muscle mass (which is lost with age) through aerobic exercise and strength training are the only ways to fight back.
尽管这是一项没有对照组的小型研究，但减肥会受到遗传和激素等多种因素的影响。其他研究表明，一些人受到遗传和激素的影响较小。有关《超级减肥王》参与者的报告引用了另一项研究。该研究表明，做过减肥手术的肥胖者似乎能够摆脱代谢适应过程。不知为何，他们的身体能够适应新的正常体重，静息代谢率也不会降低。我们其余的人，必须要对自己的饮食特别上心，通过有氧锻炼和力量训练的方法练出肌肉群(随着年龄增长会丧失)，这是防止体重反弹的唯一方法。
Your resting metabolic rate determines only a proportion of your energy expenditure. If you burn off more calories than you eat, you will lose weight. Other research suggests that reducing calories by 20% and doing moderate exercise for 20 minutes a day will keep weight off.
静息代谢率只能决定你的一部分能量消耗。如果你消耗的热量比摄入的多，你的体重就会减轻。其他研究表明，每天少摄入20%的热量，适度锻炼20分钟能够减肥。
